Pulmonary function growth velocity in children 6 to 18 years of age

Pulmonary function growth rate varies with a child's stage of growth. Since attained pulmonary function reflects the cumulative effects of growth, insults, and repair, rate of growth may be a more sensitive indicator of a child's current pulmonary health status. The sample for analyses included 2,478 white boys and 2,785 white girls followed annually by questionnaire and spirometry. Empirically derived annual growth velocities, peak velocity (V(pk)), and age at which peak velocity occurred (Age(pk)) were determined for height, FVC, FEV₁, and FEF_25-75 for each child. Mean velocity curves for height, FVC, FEV₁, and FEF_25-75, stratified by sex and Age(pk) of height (an indicator for early, middle, or late maturity) were produced as a function of age. The differences between Age(pk) of FVC, FEV₁, and FEF_25-75 and Age(pk) of height (i.e., the lag period) were compared by sex and by the indicator of maturity. Linear regression analyses were performed to investigate associations between V(pk) and Age(pk) of height, as well as between the lag period and Age(pk) of height. As is generally observed in height growth, there were considerable variations in the age of onset and magnitudes of the adolescent growth spurts of the pulmonary function parameters both between sexes and among children of the same sex. The duration of adolescent growth spurt appeared to be similar for all children, regardless of early, middle, or late maturity. Thus, those who matured earlier had shorter total growth periods than those who matured later. On the other hand, early maturers had greater growth velocities during preadolescence and greater adolescent V(pk) than later maturers. The pulmonary function growth spurt generally lagged behind the height growth spurt. The length of this lag period was on average 0.6 to 0.9 yr, but it varied with a child's age at peak height velocity. The earlier the onset of the height growth spurt, the greater the lag between height and pulmonary function growth. This analysis provides new insights to clinicians and researchers regarding the interpretation of pulmonary function measurements during the complex period of adolescent height and lung growth.